1. Field of the Invention
The invention relates to selectively improving overall image sharpness in a camera used in making pseudo format images such as pseudo telephoto format and pseudo panoramic format images. In such pseudo images, only a selected portion of the exposed film frame contains the image portion to be viewed, either directly or by printing concerned with cameras wherein the lens focus suffers from such large magnitude field curvature that the film plane is located at a compromise position in which some image sharpness at the center is sacrificed for better average overall sharpness. Such field curvature would ordinarily be encountered in a low cost lens. The invention provides means for adjusting lens focus in a simple, inexpensive manner, as the user selects the desired type of image, such that the compromise is adjusted to provide improved average sharpness in the film area which will receive the particular image type selected by the user.
2. Description of the Prior Art
I am not aware of any prior art teaching the concept of this invention. A discussion of pseudo photography can be found in U.S. Pat. No. 4,650,304, issued Mar. 17, 1987. As discussed in that patent, a pseudo telephoto print is one that is made from a central portion of an exposure having the same width-to-length ratio, e.g. 31/2:5, as that of the exposure. During the printing process, the negative is masked at its upper, lower, left and right marginal zones, leaving the central portion of the negative unobscured. Alternatively, the film gate in the enlarger may be correspondingly masked or adjusted. Then, an enlargement is made of the central portion of the negative to provide a print the same width-to-length ratio as that of the central portion. Thus, the print will have a telephoto or close-up format.
A pseudo panoramic print is one that is made from a narrow portion of an exposure having a greater width-to-length ratio, e.g., 1:3, than that of the exposure. During the printing process, the negative is masked at its upper and/or lower marginal zones, leaving a narrow portion of the negative unobscured. Alternatively, the film gate in the enlarger may be correspondingly masked or adjusted. Then an enlargement is made of the narrow portion of the negative to provide a print with the same width-to-length ratio as that of the narrow portion. Thus, the print will have a panoramic or elongate format.